Dither tuned microwave tube

ABSTRACT

The output frequency of a microwave tube, such as a magnetron, is swept back and forth (dithered) over the tunable range of the tube by means of a motor driven actuator which causes reciprocal rectilinear translation of a tuning member within the tube. The tuning actuator includes a cam having a circular cam track to receive a cam follower. The circular cam track is scalloped out of the plane of rotation such that, as the cam follower follows the track, reciprocal rectilinear translation is obtained between the cam follower and the cam. This rectilinear translation is coupled to the tuning means.

United States Patent [191 Stoke Dec. 3, 1974 DITHER TUNED MICROWAVE TUBE Primary Examiner-James W. Lawrence Assistant ExaminerSaxfield Chatmon Jr. R St k 1 C If. [75] Inventor chard C 0 Sunnyva e an Attorney, Agent, or Ftrm-Stanley Z. Cole; D. R. [73] Assignee: Varian Associates, Palo Alto, Calif. Pr s a Harry E, Ai e [22] Filed: Mar. 14, 1974 21 App]. N01: 450,964 [571 ABSTRACT 1 The output frequency of a microwave tube, such as a 1 magnetron, is swept back and forth (dithered) over 315/3951 hfi5g2g3 the tunable range of the tube by means of a motor 58 Field of Search 315/3955, 39.57, 39.59, P l whlch 93'? i f f 315/3961 39.77 trans ation o a tuning mem er Wit in t e tu e. e tuning actuator includes a cam having a clrcular cam [56] R f d track to receive a cam follower. The circular cam e erences le track is scalloped out of the plane of rotation such UNITED STATES PATENTS that, as the cam follower follows the track, reciprocal 3,441,794 4/1969 Chun 3 15/39.6l rectilinear translation is obtained between .the cam fol- 3.44lq795 4/1969 Hynes 315/39.61 lower and the cam. This rectilinear translation is cou- 3,590,313 6/1971 Stoke 315/39.6l pied to the tuning means. 3,731,137 5/1973 Foreman 315/3955 4 Claims, 3 Drawing Figures DITHER TUNED MICROWAVE TUBE BACKGROUND OF THE INVENTION The present invention relates in general to frequency agile microwave tubes and more particularly to a mechanically dithered microwave tube, such as a magnetron, of the type wherein a motor driven tuner actuator produces reciprocal rectilinear translation of the tuning member for dither tuning of the tube.

DESCRIPTION OF THE PRIOR ART Pat. Nos. 3,4l4,761 issued Dec. 3, 1968; 3,441,795 issued Apr. 29, 1969; and U.S. Pat. No. 3,590,313 issued June29, 1971.

One of the problems with this prior arrangement is that the transverse mounting of the motor at the end of the tube substantially increased the overall lengthof the tube and, in some applications, it is desirable that the overall length of the tube be substantially reduced.

Inaddition, the eccentric crankshaft, for imparting re-' ciprocal rectilinear translation to the tuning actuator, results in some whipping or flexing of the actuating member in order to accommodate the transverse motion of the eccentriccam when the eccentric is in the transverse plane. It would be desirable to devise a tuning actuator mechanism which does not result in the whipping or flexing action of the tuning actuator member and which results in a lower profile for the tube.

SUMMARY OF THE PRESENT INVENTION The principal objectofth'e present invention is the provision of an improved dither tuned microwave tube and more particularly to an improved actuator for effecting reciprocal rectilinear translation'of the tuning element within the tube. a t

In one feature of the present invention, the tuning actuator includes a cam having a circular cam track to re- I ceive a cam follower, the cam track is scalloped in a direction normal to the mean plane of the circular cam track to derive reciprocal rectilinear translation between the cam and cam follower, whereby the rectilinear translation may be coupled to the tuner for dither tuning the tube.

In another feature of the present invention, the motor i i for driving the dither tuning apparatus is mounted to the microwave tube with the axis of revolution of the drive shaft of the motor being generally parallel to the axis of rectilineartranslation of the tuning structure,

whereby the overall length of the tube is shortened as contrasted with the prior arrangement wherein the motor was mounted with its axis transverse to the axis of rectilinear translation of the tuning structure.

In another feature of the present invention, the cam follower includes a rotatable cylindrical follower riding on the circular cam track in rolling engagement there ing specification taken in connection with the accompanying drawings wherein:

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view, 'partly in section, of a dither tuned magnetron incorporating features of the present invention,

.FIG. 2 is an enlarged elevational view of the portion of the structure of FIG. 1 delineated by line 2-2, and

7 FIG. 3 is an enlarged sectional view of a portion of the structure of FIG. 1 delineated by line 3-3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1,there is shown a dither.

tuned coaxial magnetron microwave tubell incorporating features of the present invention. Microwave tube 11 is of the type generally described in the aforecited U.S. Pat. No. 3,441,795 and only partially shown herein. It includes a main body portion 22 housing a toroid-shaped cavity resonator 23 coaxially surrounding an array of vane resonators 24 which in-turn surround a cathode emitter 25 to define an annular magnetron interaction region between the vane resonators 24 and the cathode emitter 25. The vane resonators are carried at their outer edges from a cylindrical anode wall 26 forming a common wall of the resonator 23 and the vane resonator system 24. An array of longitudinally directed coupling slots 27 are provided communicating through the commonwall 26 with altematevane resonators for locking'the 1r mode of oscillation of the vane resonator system 24 to the TE circular electric mode in the coaxial cavity 23. g a

The upper end wall 28 of the cavity resonator 23 is axially movable for tuning the resonant frequency of the resonator 23 and thus the frequency of the 11' mode and the output frequency of the tube. Movable end wall 28 is carried from dependent legs 29 of a spider structure 31. The body portion 31 of the spider is an annular disc sealed to the body of the tube via a pairiof axially spaced bellows 32' and 33. The spider 31 is axially translatable via an axially directed actuating rod 34 which is affixed at its lower extremity via a nut to the bottom of a cup-shaped member 35 whichis affixed at its outer periphery to the spider 31. A fixed cylindrical slide linear motion ball bearing assembly 36 is affixed with and wherein the cylindrical follower has an axis of riphery of the cylindrical cam member 38. The recess or cam track 39 is scalloped out of the mean plane of the circular cam track indicated by line 41. In a typical example, the cam track 39 is scalloped out of the mean plane 41 with a sinusoidal variation taken around the periphery of the circular cam track 39. In the typical example, there are two sinusoidal cycles or periods taken around the periphery of the cylindrical cam 38 with a peak-to-peak displacement A of, for example, 0.021 inch of the center line 40 of the cam track relative to the mean plane of the cam track 41.

A pair of cam followers 42 are diametrically opposed of the cam 38 and are carried in a ring 43 (See FIGS. 1 and 3) coaxially mounted of the actuating rod 34 and cam 38. The ring 43 is driven by a ring gear 44 affixed to the support ring 43 and meshing with an idler gear 45 which in-turn meshes with a drive gear 46 affixed to the output drive shaft 47 of a motor 48. Radial bearings 49, 50 and 51 are mounted in a housing structure 52 to provide bearing support for the motor drive shaft 47 and idler gear shaft 53, respectively. The housing 52 is fixedly secured to the body 22 of the tube. Thrust ball bearing assemblies 55 and 56 provide thrust bearing support for the cam follower ring 43 relative to the housing 52.

The cam follower 42 includes a ball bearing-supported roller bearing 57 carried upon the inner end of a cylindrical shaft 58 which in-turn is carried from the support ring 43. The shafts 58 project radially from the ring 43 toward the actuator rod 34 in diametrically opposed positions in the ring 43. As the ring 43 is driven around the cam 38, the cam follower bearings 57 ride in the recessed cam track 39. Since the cam follower 42 is captured against axial translation via the thrust bearings 55 and 56, the cam 38 is caused to oscillate or reciprocate in a direction along theaxis of the actuator rod 34 with a displacement corresponding to the peakto-peak displacement A of the center line 40 of the cam track 39 relative to the mean plane 41 of the cam track 39 at twice the rotation frequency of the cam follower 42 around the cam 38.

in a typical example, the peak-to-peak displacement of 0.021 inch produces 250MHz frequency shift at the rate of 150Hz. An electrical generator 59 is coupled to the output shaft 47 of the motor 48 for generating an output voltage in synchronism with the frequency deviation of the output frequency of the tube 11 when the motor is operating at rated speed. This voltage is utilized in the receiver of the radar for causing the local oscillator to track the changing frequency of the transmitted output signal derived from the tube 11 being tuned.

One of the advantages to the use of the circular cam follower is that the motor may be mounted with its drive shaft 47 generally parallel to the tuner actuator rod 34 and parallel to the axis of the tube such that the motor and generator 48 and 59 do not contribute to lengthening of the overall tube structure. in addition, the actuator mechanism including the gear train driving the cam follower has a relatively low profile which permits a reduction in the height of the tube or length of the tube needed for the tuner drive mechanism. In a typical example the height of the housing 52 is reduced to approximately 0.7 inches as contrasted with 1.75 inches as required by the prior art arrangement as exemplified by the aforecited US. Pat. Nos. 3,441,795; 3,414,761 and 3,590,313. In addition, the whipping action on the actuator rod is eliminated in the design of the present invention.

What is claimed is:

1. In a dither tuned microwave tube:

cathode emitter means for emitting a stream of electrons;

microwave circuit means disposed adjacent said cathode emitter means in electromagnetic wave energy exchanging relation with the stream of electrons;

means for applying an anode potential to said microwave circuit means relative to said cathode means for drawing the stream of electrons from said cathode means towards said microwave circuit means and for generating wave energy on said microwave circuit means as a result of the electromagnetic wave interaction between the fields of said microwave circuit and the electrons of said electron stream;

tuning means for displacing electromagnetic fields of said microwave circuit means for tuning of said microwave circuit means and thus the frequency of the wave energy generated on said microwave circuit means;

said tuning means including, a tuning structure movable relative to said microwave circuit for variably displacing fields of said microwave circuit, tuner actuator means coupled to said tuning structure for effecting reciprocal rectilinear translation of said tuning structure, and motor means for imparting rotary motion to said actuator means for actuation thereof;

said tuner'actuator means including cam means having a circular cam track to receive a cam follower means, said circular cam track being scalloped in a direction normal to the mean plane of the circular cam track, and cam follower means following said circular scalloped cam track to derive reciprocal rectilinear translation of one of said cam means relative to said microwave circuit means, and means for coupling said reciprocating one of said cam means to said tuning structure to effect reciprocal rectilinear translation thereof.

2. The apparatus of claim 1 wherein said motor means includes a rotatable drive shaft, and wherein the axis of revolution of said drive shaft is generally parallel to the axis of rectilinear translation of saidtuning structure.

3. The apparatus of claim 1 wherein said cam follower means includes a rotatable cylindrical follower member riding on said cam track in rolling engagement therewith and having an axis of revolution radially directed of said circular cam track.

4. The apparatus of claim 1 wherein said reciprocating one of said cam means is said cam track means and including means for rotating said cam follower means around said scalloped circular cam track of said cam means, and means for capturing said rotatable cam follower means against reciprocal rectilinear translation, I

axial rectilinear translation of said tuning structure. 

1. In a dither tuned microwave tube: cathode emitter means for emitting a stream of electrons; microwave circuit means disposed adjacent said cathode emitter means in electromagnetic wave energy exchanging relation with the stream of electrons; means for applying an anode potential to said microwave circuit means relative to said cathode means for drawing the stream of electrons from said cathode means towards said microwave circuit means and for generating wave energy on said microwave circuit means as a result of the electromagnetic wave interaction between the fields of said microwave circuit and the electrons of said electron stream; tuning means for displacing electromagnetic fields of said microwave circuit means for tuning of said microwave circuit means and thUs the frequency of the wave energy generated on said microwave circuit means; said tuning means including, a tuning structure movable relative to said microwave circuit for variably displacing fields of said microwave circuit, tuner actuator means coupled to said tuning structure for effecting reciprocal rectilinear translation of said tuning structure, and motor means for imparting rotary motion to said actuator means for actuation thereof; said tuner actuator means including cam means having a circular cam track to receive a cam follower means, said circular cam track being scalloped in a direction normal to the mean plane of the circular cam track, and cam follower means following said circular scalloped cam track to derive reciprocal rectilinear translation of one of said cam means relative to said microwave circuit means, and means for coupling said reciprocating one of said cam means to said tuning structure to effect reciprocal rectilinear translation thereof.
 2. The apparatus of claim 1 wherein said motor means includes a rotatable drive shaft, and wherein the axis of revolution of said drive shaft is generally parallel to the axis of rectilinear translation of said tuning structure.
 3. The apparatus of claim 1 wherein said cam follower means includes a rotatable cylindrical follower member riding on said cam track in rolling engagement therewith and having an axis of revolution radially directed of said circular cam track.
 4. The apparatus of claim 1 wherein said reciprocating one of said cam means is said cam track means and including means for rotating said cam follower means around said scalloped circular cam track of said cam means, and means for capturing said rotatable cam follower means against reciprocal rectilinear translation, whereby rotation of said cam follower means around said scalloped cam track results in effecting reciprocal axial rectilinear translation of said tuning structure. 